A review of electron probe X‐ray microanalysis studies of salivary gland cells

Abstract

Electron probe X-ray microanalysis (EPXMA) has now been successfully applied to several salivary gland preparations. This paper briefly reviews the principles underlying this technique and the specific sample preparation procedures which permit accurate measurement of elemental concentrations in the various intracellular spaces. Findings from salivary gland studies indicate that cytoplasmic and nuclear spaces of nonstimulated acinar cells have high concentrations of K and P, and low concentrations of Mg, Ca, and S; and that mature secretory granules have high concentrations of Ca and S, and relatively low concentrations of K and P. No consistent differences have been found between the elemental concentrations of mucous and serous secretory granules. In vivo and in vitro EPXMA studies of the elemental changes associated with secretory granule maturation indicate there are at least two stages in this process: an early stage during which granule S concentration increases in parallel with mass density as condensing vacuoles mature into secretory granules, and a late stage during which granule mass density and protein content increase with no further elemental concentration changes. Findings from other in vivo and in vitro studies indicate that secretory granule membranes are permeable to Na, K, and Cl ions because the granular concentrations of these elements are altered by electrochemical gradients. Recent EPXMA results indicate that cells stimulated with parasympathomimetic agonists have decreased K and Cl concentrations, and increased Na concentrations. Furthermore, the magnitude of these changes are quantitatively consistent with changes measured using radio-isotope equilibration and other techniques. In contrast, cells stimulated with the beta-adrenergic agonist, isoproterenol, have increased concentrations of Na and Cl, but unchanged K concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloride secretion in the submandibular gland of adult and early postnatal rats studied by X-ray microanalysis

“…3A). Studies on thin sections (Sasaki et al 1983;Izutsu et al 1985Izutsu et al , 1994Izutsu and Johnson 1986) also demonstrated that secretory granules typically have higher concentrationss of Ca, and lower concentrations of P and K than the cytoplasm and nucleus. Also in the apical cytoplasm, the concentrations of these elements decreased (data not shown).…”

“…X-ray microanalysis has been used to study ion distribution in salivary glands under unstimulated and stimulated conditions (Roomans et al 1989;Izutsu et al 1994) and the method has been shown to provide useful information on m o v e m e n t s of ions as a result of stimulation. X-ray microanalysis has been used to study ion distribution in salivary glands under unstimulated and stimulated conditions (Roomans et al 1989;Izutsu et al 1994) and the method has been shown to provide useful information on m o v e m e n t s of ions as a result of stimulation.…”

Ontogeny of guanylin-immunoreactive cells in rat salivary glands

“…acinar/pro-acinar cells, terminal duct cells and serosal demilunes) guanylin immunoreactivity was more widespread within the cells, and, in the submandibular gland, concentrated at the apical side. We observed intense guanylin immunoreactivity at the earliest stages of acinar development, when salivary secretion and ion and fluid transport were defective or minimal (Martinez and Camden 1989;Mork et al 1996;Izutsu et al 1994). In the adult lifetime, this intense activity decreased until it almost disappeared.…”

Effects of cholinergic and α-adrenergic agonists on the monovalent ion content of rat submandibular gland acinar cells studied by X-ray microanalysis

“…This suggests that the limiting membranes are permeable to these ions to the extent that there is a quick equilibration among the various organelles (Gasser et al 1988;Izutsu et al 1994). All the organelles lose K and Cl upon stimulation, including secretory granules.…”

“…The ionic mechanisms underlying fluid secretion from rat submandibular glands have been studied using both in vivo (Sasaki et al 1983;Izutsu et al 1994) and in vitro preparations (Martinez andCassity 1983, 1985). The presence of neural tissue and extracellular elements imposing diffusional barriers complicates the interpretation of experimental results in the in vivo preparation, while changes in cells during isolation and differences in the microenviroment in which isolated cells are studied could alter the response to agonists in the in vitro studies.…”